A comparison of data reduction techniques for the aero-acoustic analysis of flow over a blunt flat plate

A large eddy simulation of flow over a forward-facing plate is performed and the resulting database analyzed with respect to sound radiation. Aero-acoustic analysis motivates an initial data compression comprising eduction of the zeroth-order spanwise Fourier mode. The space-time structure of this component of the flow is then analyzed using POD and DMD in order to probe both the energetics and dynamics of the sound producing flow skeleton. Both data processing techniques educe flapping and shedding modes and identify a nonlinear interaction between the two. POD shows the flapping mode to be energetically unimportant, while DMD highlights its dynamic importance. The difference mode-vortex shedding modulated by flapping of the separation bubble is found to be the most acoustically important feature of the flow. (authors)